A double-blind comparison of two creams containing urea as the active ingredient. Assessment of efficacy and side-effects by non-invasive techniques and a clinical scoring scheme.Acta Derm Venereol Suppl (Stockh). 1992; 177:34-43.AD
From a group of 72 healthy individuals, 47 with evidence of dry skin according to measurements by non-invasive techniques were enrolled for a 3-week study with double-blind and randomized treatment of one forearm, using either 3% urea cream (HTH lotion 'light') or 10% urea cream (HTH lotion 'Original'). The contralateral forearm served as an untreated control. Two volunteers had to be excluded because measurements of skin surface lipids gave evidence of vehicle components on the skin surface at the time of final evaluations. Evaluations took place not less than 12 h after the last application. According to questionnaire replies, the two creams were equally effective. This was confirmed by "blind" evaluation of the skin hydration state by a dermatologist, measurements of electrical capacitance and conductance indicating epidermal and skin surface hydration, and by D-Squame tape assessments including optical transmission of tapes with stratum corneum and scales from adhering skin, as well as visual scoring of the tapes. The methods showed a high degree of correlation, i.a. a definite relation between increase in electrical hydration parameters, reduced scaling according to the D-Squame tape evaluations, and clinical improvement of dryness. In skin treated with 10% urea cream the transepidermal water loss (TEWL) decreased, indicating an improved water barrier function. Skin colour measurement according to the CIE colour system showed that skin treated with the 3% urea cream turned in the direction of yellow, and there was generally a tendency for the brightness to decrease. Thus, the 3% urea cream gave the skin a more golden colour. There was no change in redness with any of the creams. Neither data from the questionnaire, the clinical examination, nor results of TEWL and colour measurements indicated any local irritant effect of urea causing water barrier damage or inflammation. In conclusion, the 3% and 10% urea creams were both found efficient, resulting in improvement of hydration and reduction of scaling. Both were non-toxic. However, specific differences did appear, viz. the 3% urea cream turned the skin colour golden, while the 10% urea cream improved the skin's water barrier function.